1. Field of the Invention
The present invention is broadly concerned with improved, two-component systems and methods for removing proteinaceous soils from surfaces, including an enzymatic prewash and an acidic secondary wash. More particularly, the invention is concerned with such systems and methods which are especially suited for clean-in-place (CIP) treatment of dairy equipment subject to milk-borne contamination, wherein the initial prewash includes a protease enzyme, preferably in combination with a polyol, whereas the secondary acid wash includes an acid, advantageously combined with a surfactant.
2. Description of the Prior Art
During dairy processing of milk, heat sterilization is performed in order to prevent microbial contamination. However, this inevitably causes deposition of milk-borne proteinaceous materials onto the surfaces of the dairy equipment. Such proteinaceous soils are extremely tenacious and are difficult to remove without a combination of a strong oxidizer combined with high levels of alkalinity for fat removal. The most common oxidizers in use today are chlorine-based materials. However, chlorine oxidizers present environmental problems, and there is an ongoing effort to find substitute, non-chlorinated cleaning agents which match or exceed the cleaning power of the chlorinated materials while avoiding the adverse environmental impact thereof.
Most dairies employ the CIP method, involving flushing of contaminated equipment surfaces with cleaning solution(s). For example, in conventional practice, the equipment is rinsed with lukewarm (110-120xc2x0 F.) water followed by a hot was using a chlorinated agent at 160-175xc2x0 C. The last step is commonly a cold acidic rinse using a phosphoric acid-based wash. The necessary tanks, pumps and control hardware for CIP processes are thus presently in place in the dairies. It is therefore highly desirable that any new cleaning system or method be usable in a CIP context without the need for any significant modifications of the in-place equipment.
A number of researchers have examined the utility of enzyme treatments as primary cleaning products, see e.g., U.S. Pat. Nos. 4,212,761, 5,858,117, 4,243,543, 5,510,052, 5,783,542,5,489,531,6,071,356 and 5,861,366. However, these references do not deal with commercial methods and systems where an enzymatic treatment is followed by an acid wash.
The present invention overcomes the problems outlined above and provides cleaning methods and systems especially designed for the removal of proteinaceous soils from surfaces. The invention finds particular utility in the CIP treatment of dairy equipment in lieu of conventional chlorinated cleansers. Broadly speaking the method of invention involves initially contacting soiled surfaces with a first aqueous use dispersion including a protease enzyme and preferably (but not necessarily) a polyol therein. After such initial treatment, the surface is thereafter contacted with a second aqueous use dispersion including an acid such as phosphoric acid; the second use dispersion preferably includes a surfactant therein.
The initial and second contacting steps are advantageously carried out for a period of from about 2-15 minutes, more preferably from about 5-10 minutes. Normally, both of the use dispersions are heated to a level above ambient, although this is not essential. In practice, both of the dispersions are simply circulated for contact with soiled surfaces; for example, in CIP cleaning, the use dispersions are circulated in a manner essentially identical with the conventional practice.
Dispersions in accordance with the invention (as used herein, xe2x80x9cdispersionsxe2x80x9d refers to any type of aqueous mixture, be it a true solution, a colloid, an emulsion or a dispersion) are typically provided in the form of concentrates which can be diluted on-site at the time of use. Moreover, the enzyme prewash and acid wash components are preferably provided to the consumer as a system designed to operate in tandem for the most efficient cleaning.
The following example sets forth preferred enzyme prewash/acid wash systems and treatments in accordance with the invention. It is to be understood, however, that this example is provided by way of illustration and nothing therein should be taken as a limitation upon the overall scope of the invention.